|Wind energy -not proven|
It comes as scrutiny increases on other more high profile failures in the renewable energy sector. Solyndra in the US for example, has filed for bankruptcy despite very significant government investment and loans.
This seems like a good time to look at some figures. The UK currently has around 3,500 wind turbines with a capacity of 5.5 gigawatts of electricity. As far as I can ascertain they only contribute to the grid between 0.5 and 1.0 gigawatts for the grid at any one time amounting to between 1.5% and 2.5% of demand. The installation cost of these wind turbines is around £7bn - rather more that the cost to build a few power stations with other means of generating electricity.
Much of that 'investment' comes from public subsidies. All of which leaves Alex Salmond's vision of 100% of Scotland's electricity from green sources looking both expensive and uncertain as Struan Stevenson's article here points out.